The invention relates in general to storage containers for devices containing energetic material and in particular to storage containers that meet insensitive munitions (IM) requirements.
Containers may be used to store devices containing energetic material. For example, ammunition containers may be used to store one or more munitions. The munitions may contain energetic material that may produce gas when subjected to unplanned stimuli. This gas may require a way to escape from the ammunition container in a non-violent way. Ammuntion containers for munitions may be required to comply with Insensitive Munitions (IM) requirements set forth in MIL-STD-2105C and Ammunition Packaging requirements set forth in MIL-STD-1904A.
Regarding IM requirements, two tests may be used to simulate ammunition containers exposed to a fire, a slow cook off test (SCO) and a fast cook off test (FCO). In SCO, an ammunition container containing one or more munitions may be heated at a rate of 6° F./hour until the munition reacts. In FCO, an ammunition container containing one or more munitions may be engulfed in a flame of at least 800° C. until the munition reacts. It may be desirable for the reaction to be limited to no more than burning (Type 5 reaction). A detonation (Type 1 reaction) may not be acceptable.
One way to comply with IM requirements for ammunition containers is to include a venting window in the ammunition container. High pressure and/or temperature produced by munitions in the ammunition container may cause the venting window in the ammunition container to rupture or open, thereby releasing the high pressure gas before the munition in the container undergoes a violent reaction. But, the venting window must be strong enough to meet rough handling requirements for ammunition containers. Before and after the rough handling tests, the ammunition container must be able to contain an internal air pressure of at least three psi with a leakage rate of no more than five cc/minute.
Venting windows have been successfully used in ammunition containers such as the Modular Artillery Charge System (MACS) ammunition container. For the MACS container, the venting window was made of a glass-filled ionomer plastic. To pass rough handling tests, the ionomer plastic had to be at least 40% glass-filled. Ionomer plastic vent windows with a glass fill higher than 40% were found to inhibit the venting of the window. When the venting window of the MACS container was used in other ammunition containers, such as, for example, a PA19 container, the vent window failed to open during cook off tests. Reducing the percentage of glass fill in the venting window or decreasing the thickness of the venting window allowed the venting window to rupture. On the other hand, neither the reduced-glass content venting window nor the thinner venting window passed the rough handling requirements.
A need exists for a storage container for devices with energetic material wherein the storage container meets both IM requirements and rough handling requirements.